Understanding the Social Factors Associated with Congenital Syphilis

In recent years, syphilis cases have been increasing, and there has been a surge in cases among newborns. Syphilis is a sexually transmitted infection caused by the Treponema pallidum. It can be passed during vaginal, anal, or oral sex. It can also be passed from a mother to an infant during pregnancy or delivery. This is referred to as congenital syphilis.

There were 3,755 babies born with congenital syphilis in 2022 alone. This is over 10 times more babies than were born with syphilis in 2012. Public health experts have said that every case of congenital syphilis is a failure of STI screening and prenatal care. A new study looked more closely at cases to see what factors in a pregnant person’s life were most associated with congenital syphilis.

The study, by researchers at Washington University’s Institute for Public Health, looked at five years of medical records for mother/infant pairs in Missouri. Pairs were included in the analysis if the child had a positive RPR test (which looks for syphilis antibodies in the blood but often gives false positives) or other mention of syphilis in their medical charts.

Researchers initially identified 130 pairs. Further examination of their medical records led researchers to believe that 74 of the infants in these pairs were likely born with congenital syphilis and 56 were likely not. Among mothers of infants who had congenital syphilis:

• 47% had limited or no prenatal care
• 42% had a history of substance abuse
• 25% had housing instability
• 8% had history of transactional sex

When compared to mothers of infants who likely did not have congenital syphilis, the potential congenital syphilis group was more likely to:

• be uninsured (12% v 4%),
• have a history of inadequate prenatal care (60% vs 31%),
• have a history of substance use (54% vs 27%),
• have experienced housing instability (34% vs 14%), and
• have had previous interactions with justice system (32% vs 20%).

Researchers found that inadequate prenatal care and housing instability were the best predictors of congenital syphilis outcomes. Of course, all of these factors are interrelated. Mothers with substance use, for example, are more likely to have inadequate prenatal care. Other factors that related to inadequate prenatal care were unemployment, lacking of insurance, and a history of transactional sex.